[0031]According to the method of par. 1), there can be manufactured a pipe coupling component including a semi-tubular portion which is to come into close contact with a half of the outer circumferential surface of a pipe, and flat portions which are integrally formed along opposite side edges of the semi-tubular portion and are located on a common plane, in which edge portions are formed, rather than round portions, at the boundaries between the inner circumferential surface of the semi-tubular portion and the surfaces of the flat portions facing the direction toward which the semi-tubular portion is open. Accordingly, when two pipe coupling components manufactured by this method are combined such that the openings of their semi-tubular portions face each other, it is possible to prevent formation of a relatively large clearance between the inner circumferential surface of a tubular portion formed by the two semi-tubular portions and the outer circumferential surface of the pipe inserted into the tubular portion. As a result, it is possible to prevent leakage of fluid from a product formed from the two pipe coupling components.
[0032]According to the method of par. 2), the size of the burrs of the fifth intermediate product produced in the fifth step of the above-described method of par. 1) can be set to such a size that, through removal of the burrs in the sixth step of the method, edge portions can be formed, without fail, at the boundaries between the inner circumferential surface of the semi-tubular portion and the surfaces of the flat portions facing the direction toward which the semi-tubular portion is open, and that the amount of the material to be removed can be minimized.
[0033]According to the method of par. 3), there can be produced an upper structural member including a top wall forming portion that forms the top wall of the casing main body, a circumferential wall forming portion that forms the upper half portion of the circumferential wall of the casing main body, a base portion forming portion that forms the upper half portion of the base portion of the fluid passage section, a semi-tubular coupling portion forming portion that forms the upper half portion of the pipe coupling portion of the fluid passage section, and flat portions integrally formed along opposite side edges of the coupling portion forming portion and being located on a common plane, in which edge portions are formed, rather than round portions, at the boundaries between the inner circumferential surface of the coupling portion forming portion and surfaces of the flat portions facing the direction toward which the coupling portion forming portion is open. Further, there can be produced a lower structural member including a bottom wall forming portion that forms the bottom wall of the casing main body, a circumferential wall forming portion that forms the lower half portion of the circumferential wall of the casing main body, a base portion forming portion that forms the lower half portion of the base portion of the fluid passage section, a semi-tubular coupling portion forming portion that forms the lower half portion of the pipe coupling portion of the fluid passage section, and flat portions integrally formed along opposite side edges of the coupling portion forming portion and being located on a common plane, in which edge portions are formed, rather than round portions, at the boundaries between the inner circumferential surface of the coupling portion forming portion and surfaces of the flat portions facing the direction toward which the coupling portion forming portion is open. Accordingly, when the upper and lower structural components manufactured by this method are combined such that the openings of their coupling portion forming portions face each other, it is possible to prevent formation of a relatively large clearance between the inner circumferential surface of the pipe coupling portion formed by the two coupling portion forming portions and the outer circumferential surface of the pipe inserted into the pipe coupling portion. As a result, it is possible to prevent leakage of fluid from a casing formed from the upper and lower structural members.
[0034]According to the method of par. 4), the size of the burrs of the fifth intermediate product produced in the fifth step of the above-described method of par. 3) can be set to such a size that, through removal of the burrs in the sixth step of the method, edge portions can be formed, without fail, at the boundaries between the inner circumferential surface of the coupling portion forming portion and the surfaces of the flat portions facing the direction toward which the coupling portion forming portions is open, and that the amount of the material to be removed can be minimized.
[0035]According to the pipe coupling structure of par. 5), a first outward extending flange is provided at a distal end portion of the pipe coupling portion to surround the two coupling portion forming portions; the outer circumferential edge of the first outward extending flange is located outward of the boundaries between the inner circumferential surface of each coupling portion forming portion and the surfaces of the corresponding flat portions facing a direction toward which the coupling portion forming portion is open; the pipe includes a to-be-inserted portion which is inserted into the pipe coupling portion, and a second outward extending flange provided on the outer side of the to-be-inserted portion; a coupling auxiliary member is disposed between the first outward extending flange on the hollow component side and the second outward extending flange of the pipe, and is brazed to the two outward extending flanges; and the coupling auxiliary member covers at least portions of end surfaces of the flat portions formed on the coupling portion forming portions of the pipe coupling portion, the end surfaces being located on the side toward the first outward extending flange. Therefore, even in the case where round portions are formed at the boundaries between the inner circumferential surface of each coupling portion forming portion and the surfaces of the corresponding flat portions facing the direction toward which the coupling portion forming portion is open, and, as a result, a relatively large clearance is formed between the inner circumferential surface of the tubular pipe coupling portion formed by the coupling portion forming portions and the outer circumferential surface of the pipe inserted into the pipe coupling portion, the coupling auxiliary member closes the open end of the clearance located on the side toward the first outward extending flange. Accordingly, leakage of fluid from the hollow component can be prevented.
[0036]According to the pipe coupling structure of par. 6), a first outward extending flange is provided at a distal end portion of the pipe coupling portion to surround the two coupling portion forming portions; the outer circumferential edge of the first outward extending flange is located outward of the boundaries between the inner circumferential surface of each coupling portion forming portion and the surfaces of the corresponding flat portions facing the direction toward which the coupling portion forming portion is open; the pipe includes a to-be-inserted portion which is inserted into the pipe coupling portion, and a second outward extending flange provided on the outer side of the to-be-inserted portion; the first outward extending flange and the second outward extending flange are brazed together; and the outer circumferential edge of the brazing region where the first and second outward extending flanges are brazed together is located outward of the boundaries between the inner circumferential surface of each coupling portion forming portion and the surfaces of the corresponding flat portions facing the direction toward which the coupling portion forming portion is open. Therefore, even in the case where round portions are formed at the boundaries between the inner circumferential surface of each coupling portion forming portion and the surfaces of the corresponding flat portions facing the direction toward which the coupling portion forming portion is open, and, as a result, a relatively large clearance is formed between the inner circumferential surface of the tubular pipe coupling portion formed by the coupling portion forming portions and the outer circumferential surface of the pipe inserted into the pipe coupling portion, the second outward extending flange closes the open end of the clearance located on the side toward the first outward extending flange. Accordingly, leakage of fluid from the hollow component can be prevented.